Urban air pollution and in vitro fertilization outcomes: A Canadian retrospective study.

There is growing data to support an adverse relationship between air pollution and fertility. Many studies have shown that traffic-related air pollution, the most common source of urban air pollution in North America, has a negative effect on both spontaneous and IVF pregnancy outcomes. This single-center retrospective study is the first Canadian study to explore urban air pollution exposures and IVF/ICSI outcomes. It included autologous IVF/ICSI outcomes from both fresh (ET - n = 1756) and frozen embryo transfer (FET - n = 1535) cycles between 2000 and 2022. Air pollution data for fine particulate matter (PM2.5) and nitrogen dioxide (NO2) were obtained from The Canadian Urban Environmental Health Research Consortium (CANUE). Data was analyzed using bivariate maps of long-term air pollutant exposure (PM2.5 and NO2) and IVF/ICSI clinical outcomes by 5 km2 urban areas. We found that long-term air pollution within patients' household area ranged from 4.8 to 12.6 μg/m3 for PM2.5 and 3.2-28 ppb for NO2. Nitrogen dioxide has demonstrated an association to some IVF/ICSI outcomes, which agrees with other international studies. No statistical associations in IVF/ICSI outcomes were found after adjusting for confounding variables. Understanding of the impact of urban air pollution on fertility and IVF/ICSI outcomes warrants further research on interventions to ameliorate negative outcomes and supports policy change(s) to improve air quality in the future.